Preparing to install the Mocha test framework

Download and install Node.js. The runtime environment is required for two reasons:

The Mocha test framework is started through Node.js.

NPM, which is a part of the runtime environment, is also the easiest way to download the Mocha test framework.

If you are going to use the command line mode, make sure the path to the parent folder of the Node.js executable file
and the path to the npm folder are added to the PATH variable.
This enables you to launch the Mocha test framework and npm from any folder.

Installing Mocha globally

Global installation makes a test framework available at the IntelliJ IDEA level so it can be used in any IntelliJ IDEA project.
Moreover, during installation the parent folder of the test framework is automatically added to the PATH variable,
which enables you to launch the test framework from any folder.
To install the test framework globally, do one of the following:

Run the installation from the command line in the global mode:

Launch the embedded Terminal
by hovering your mouse pointer over in the lower left corner of IntelliJ IDEA and choosing Terminal from the menu
(see Working with Embedded Local Terminal for details).

Switch to the directory where NPM is stored or define a PATH variable for it so it is available from any folder,
see Installing NodeJs.

Type the following command at the command line prompt:

npm install -g mocha

The -g key makes the test framework run in the global mode.
Because the installation is performed through NPM, the Mocha test framework is installed in the npm folder.
Make sure this parent folder is added to the PATH variable. This enables you to launch the test framework from any folder.

Run NPM from IntelliJ IDEA using the Node.js and NPM page of the Settings dialog box.

Open the Settings / Preferences Dialog by pressing Ctrl+Alt+S or by choosing File | Settings for Windows and Linux or
IntelliJ IDEA | Preferences for OS X,
and
click Node.js and NPM under Languages&Frameworks.

On the Node.js and NPM page that opens, the Packages area shows all the Node.js-dependent packages
that are currently installed on your computer, both at the global and at the project level.
Click .

In the Available Packages dialog box that opens, select the required package to install.

Select the Options check box and type -g in the text box next to it.

Optionally specify the product version and click Install Package to start installation.

Installing Mocha in a project

Installing a test framework in a specific project restricts its use to this project.
To run project installation, do one of the following:

Run the installation from the command line:

Launch the embedded Terminal
by hovering your mouse pointer over in the lower left corner of IntelliJ IDEA and choosing Terminal from the menu
(see Working with Embedded Local Terminal for details).

Switch to the project root folder and type the following command at the command line prompt:

npm install mocha

Run NPM from IntelliJ IDEA using the Node.js and NPM page of the Settings dialog box.

Open the Settings / Preferences Dialog by pressing Ctrl+Alt+S or by choosing File | Settings for Windows and Linux or
IntelliJ IDEA | Preferences for OS X,
and
click Node.js and NPM under Languages & Frameworks.

On the Node.js and NPM page that opens, the Packages area shows all the Node.js-dependent packages
that are currently installed on your computer, both at the global and at the project level.
Click .

In the Available Packages dialog box that opens, select the required package.

Optionally specify the product version and click Install Package to start installation.

Project level installation is helpful and reliable in template-based projects
of the type Node Boilerplate or Node.js Express, which already have the node_modules folder.
The latter is important because NPM installs the Mocha test framework
in a node_modules folder. If your project already contains such folder, the Mocha test framework is installed there.

Projects of other types or empty projects may not have a node_modules folder.
In this case npm goes upwards in the folder tree and installs the Mocha test framework
in the first detected node_modules folder. Keep in mind that this detected node_modules folder may be outside your current project root.

Finally, if no node_modules folder is detected in the folder tree either,
the folder is created right under the current project root and the Mocha test framework is installed there.

In either case, make sure that the parent folder of the Mocha test framework is added to the PATH variable.
This enables you to launch the test framework from any folder.